Fig. 15.—Head of the early ancestor of elephants—Meritherium—as it appeared in life. Observe the absence of a trunk and the enlarged front tooth in the upper jaw, which is converted in later members of the elephant-stock or line of descent into the great tusk. (After a drawing by Prof. Osborne.)
We now know the complete series of steps connecting elephants with ordinary trunkless, tuskless mammals. The transition from the "beast of Meris" on the one hand to the common typidentate mammalian ancestor, and on the other hand to the elephants, is easy, and requires no effort of the imagination. His short muzzle (upper and lower jaw), first elongated step by step to a considerable length, giving us Palæomastodon (Fig. 13). Then the lower jaw shrunk and became shorter than it was at the start, and the rest of the muzzle (the front part of the upper jaw, carrying with it the nostrils), drooped and became the mobile muscular elephant's trunk!
[5] I am inclined to think that the line between Pliocene and Pleistocene or Quaternary ought, in this country, to be drawn between the White and Red Crag of Suffolk. Glacial conditions set in and were recurrent from the commencement of the Red Crag deposit onwards.
[6] Mammals having the number and form of teeth which I have just described as typical—or such modification of it as can easily be produced by suppression of some teeth and enlargement of others—are called Typidentata. On the other hand, the whales, the sloths, ant-eaters, and armadilloes, as also the Marsupials, are called Variodentata, because we cannot derive their teeth from those of the Typidentate ancestor. They form lines of descent which separated from the other mammals before the Typidentate ancestor of all, except the groups just named, was evolved.
CHAPTER VII
A STRANGE EXTINCT BEAST